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by
A.
Dan
S.
I.
Feldman
D.
N.
Serpanos
Evolution
and challenges
in multimedia
This paper outlines the challenges and issues
in developing multimedia-based application
programs and solutions.
It
provides a brief
history of multimedia-based applications and a
critical perspective of the research issues that
should be addressed in the future.
Introduction
The integration of multiple media, e.g., voice, video,
image, and data, provides an effective means of
communication to the users of various services. Because
of the advances in computer and communication
technologies, creating sophisticated multimedia user
interfaces is
no
longer limited to special-purpose
applications. The popularity of the World Wide Web,
where most applications currently utilize images and data,
is adequate testimony to this fact. The increasing power of
electronic circuitry in workstations, personal computers,
and consumer electronics, in conjunction with the
decreasing cost of high-bandwidth and low-latency
communication, have created a large momentum to
develop sophisticated multimedia applications as well as to
provide new types of services to businesses and homes.
These capabilities involve improving user interfaces to
many traditional applications as well as creating futuristic
applications such as
virtual environments
and
augmented
reality
[l].
The basic idea behind the latter types of
applications is to immerse a user in an imaginary,
computer-generated
virtual world
or to augment the real
world (i.e., via augmentation
of
human perception by
supplying information not ordinarily detectable by human
senses) around a user with superimposed computer
graphics projected onto the walls
or
onto a head-mounted
display. In another example (referred to as
telepresence),
a multitude of stationary cameras mounted at a remote
environment are used to acquire both photometric and
depth information.
A
virtual environment is then
constructed in real time and redisplayed in accordance
with the local participant’s head position and orientation.
This allows local users to interact with other remote
individuals (say, with a medical consultant) as if they
were actually within the same space.
The evolution of multimedia applications can be traced
through three major stages. First, even prior to the
deployment of delivery-network infrastructure, stand-alone
applications (e.g., video arcade games) and
CD-ROM-
based applications had successfully integrated multiple
media, mostly in the form of games, entertainment, and
educational materials.
Next, high expectations of technological breakthroughs
to make available lower-cost delivery bandwidth (as
needed for sophisticated multimedia applications) created
a tremendous excitement in the area of multimedia. The
potential for the convergence of multiple services
(e.g., TV, movie, and telephone) had stirred up the
marketplace. Almost every day, newspaper headlines
announced new field trials and potential mergers of
corporations. The focus in multimedia shifted to the
creation of large-scale video servers and delivery
infrastructure that would be capable of delivering
thousands
of
simultaneous high-quality video streams to
homes and businesses. However, the economics of the
marketplace has run counter to these high expectations.
For example, in movie-on-demand applications, the cost of
storage of a large video library and the cost of delivery
Wopyright
1998
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1998
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A DAN,
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e.g.,
VCR control features will be provided by the
mechanism of copying a broadcast stream to the local disk
of
a
client or of switching to
a
different broadcast channel
with later playback of the same material. (Of course, any
local copying must take into account the protection of
intellectual property rights.)
however, is on the creation of multimedia content that can
be delivered inexpensively by means of the existing low-
bandwidth networking infrastructure as well as on the
development of platform-independent applications that
can adapt to heterogeneity in environments arising from
the differences in capabilities of system components and
end-user devices. The new forms of content fall into two
categories: low-bandwidth, real-time conferencing, and
The primary focus of current research activities,
Distribution
server andor
intelligent
network
component
Multimedia application environment.
quality of the presentation will change (i.e., dynamically
bandwidth for a two-hour video per customer were found
to be prohibitively expensive in comparison with
traditional movie rentals. In addition, the infrastructure
for delivering high-quality video was mostly unavailable,
particularly to the home. This issue is referred to as the
last-mile bandwidth problem.
Compounding this problem,
most available multimedia contents were created as
movies. Video-on-demand applications lacked the depth of
content (complexity of presentation) and provided only
limited interactivity (e.g., VCR control operations) as
compared to Web-based applications. New forms of
content have to be created to provide marketable services
to users (e.g., distance learning, travel, advertisement,
electronic commerce). Furthermore, sophisticated tools
must be available for easy creation of such multimedia
contents.
The popularity of the Web, which can
use
very low-
bandwidth networks in the last mile, and the lack of
deployment of large-scale video servers have laid the
groundwork for the current stage of multimedia.
Applications using high-bandwidth multimedia streams
will be deployed in enterprise (high-bandwidth-network)
environments and more slowly (as higher-bandwidth
infrastructure is deployed) for residential consumers. Such
services will likely follow the near-video-on-demand
(NVOD) model [2] in which a large number of clients can
share
a
set of broadcast channels, rather than the video-
on-demand (VOD) model, which requires an individual
stream per client. For example, the Digital Satellite
System (DSS) broadcasts (via satellite) a large number of
entertainment streams to its paid subscribers.
In
time,
these services will evolve to include NVOD-like features;
A. DAN,
S.
FELDMAN, ANI1 D.
N.
SERPANOS
audio quality to information delivery. Video-conferencing
applications, for example, are replacing special video-
conferencing rooms (which have high operational cost)
used in many business environments, and bringing the
desired functionality to the desks.
Challenges in multimedia-system design
Efficient multimedia systems are not just simple extensions
of conventional computing systems. Delivery of
time-
sensitive
information, such
as
voice and video, and
handling of large volumes of data require special
considerations to produce successful widespread
applications. Consequently, all system components, e.g.,
storage, operating systems, and networks, must support
these additional requirements. This results in very
different architectural and design decisions in all
subsystems and their services. More specifically, some
of the important issues that have to be addressed
when one is designing
a
multimedia system are
Storage organization and management.
Available physical bandwidth in the delivery path to the
Quality-of-service (QoS) management (real-time delivery
Information management (indexing and retrieval).
User satisfaction.
Security (especially management of content rights).
users.
and adaptability to the environment).
A generalized environment supporting multimedia
applications to homes or to business environments is
shown in
Figure
1,
in which
U1
represents the user at
home having access to an application or service through
an access network, while
a
business user (U2) is connected
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through
a
local area network, i.e., a customer-premises
network. A multimedia server delivers services (i.e.,
multimedia data streams) over
a
series of (possibly)
heterogeneous networks to the clients. (Further processing
can take place within the network, e.g., multicasting,
transformation of content.) As the figure illustrates, the
need to provide flawless service to users places significant
requirements on a large number of components, which
have to work well together. In order to cope with the
complexity of several heterogeneous systems involved in
the end-to-end service, one can systematically analyze the
components in order to evaluate various options and the
design challenges. The design issues are broadly classified
into the following categories:
1. Server subsystems that store, manage, and retrieve the
multimedia data stream(s) upon a user request.
2.
Network subsystems that transport, deliver, adapt (and
perhaps transform) the data streams isochronously (Le.,
at a specified rate, without observable delay) to the
clients.
3. Client subsystems that receive and/or prefetch the data
streams and manage the presentation of data.
4. Application programs that deal with relationships
among data frames and media segments, and manage
user
navigation and retrieval of this data.
Multimedia technology has to address all of the
components in coordination, since each component has
evolved individually up to now. The following sections
describe some of the major challenges to be overcome for
modern multimedia applications to become ubiquitous and
as
influential as we predict. The discussions are not
intended to be exhaustive, but to refer to significant
research activities that are described in this issue of the
IBM
Journal
of
Research and Development
or are under
way at IBM and elsewhere. For a broader introduction to
and survey of the multimedia area, the readers should
refer to a companion paper in this issue [3].
Server-design issues
Multimedia servers store and manage multimedia
documents and deliver data streams in an isochronous
manner, in response to delivery requests from users. They
may also process the stored information before delivery to
users. In the future, multimedia servers may range from
low-cost, PC-based simple servers that deliver a few
streams, to scalable large (either centralized or distributed
[4,
51)
servers that will provide thousands of streams. The
content may range from long, sequentially accessed videos
to composite documents consisting of a mixture of small
multiple-media segments (e.g., video, audio, image, text).
The multimedia objects that are large and are played
back sequentially require relatively large storage space and
playback bandwidth. Therefore, considerable initial
research has been directed toward a) efficient retrieval
of
data from disks, in order to amortize seek time and to
avoid
jitter
[6],
b)
striping
of data across storage devices
for load balancing [7], and c) scheduling of system
resources to avoid jitter
[8-lo].
Retrieval of large data
blocks
is
now a well-accepted practice in most commercial
servers [7, 81. The
use
of
double buffering
to improve
bandwidth utilization without incurring jitter can be cost-
effective
[ll].
While simple striping is effective for load
balancing across a set of homogeneous storage devices for
long sequential accesses, complex
block-allocation
policies
that take into account bandwidth and storage capacities of
the devices are necessary. An alternative approach is to
partition the storage devices into sets of homogeneous
striping groups. A higher-level policy assigns media objects
to these devices, matching the storage and bandwidth
requirements of the documents to the availability of those
in the striping groups
[12].
Another related problem is
dynamic load balancing
across servers or striping groups
[13]. For example, in [14] a policy of temporarily
replicating “hot” data segments (i.e., frequently accessed
parts of the media objects) by copying retrieved data in
playback streams is used to dynamically balance the
load across striping groups. Such a dynamic policy is
complementary to the initial data-placement policy.
The low-cost servers that are designed to serve a few
dozen streams may be simple, PC-based servers and may
not employ various resource-optimization techniques
(other than retrieval of large data blocks). However, large-
scale servers that can serve thousands
of
streams exploit
the economies of scale and can
be
quite complex [8]. For
example, in a video-on-demand server, multiple requests
for the same popular video that arrive within a short time
period can be
batched
for service by a single playback
stream. Various video-scheduling policies take into
account user satisfaction while improving effective server
capacity [15]. Another optimization technique known as
bridging
speeds up the following streams while slowing
down the preceding streams for the same video in order to
achieve an eventual merging of these streams, and hence
to avoid multiple playback streams [16]. The main memory
buffer of the server can be used to cache retrieved data
for later playback. A technique known as
interval caching
uses buffers to cache the short intervals between
successive playback streams of the same video [17]. This
caching can also be used for balancing changing loads
across storage devices [17].
To guarantee
QoS
and avoid jitter, multimedia servers
employ admission control; i.e.,
a
new request is granted
only
if
enough server resources are available. This implies
that a video server has to know in advance the number of
streams it can serve without jitter. The capacity of a video
server can be expressed in statistical terms, e.g., the
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Table
1
Network layers.
Multimedia application
(OS1
6-7)
Transport
(OS1
4-5-6)
Network
Data-link control
Physical
number of streams it can serve with a certain level of jitter
[ll]. For a server complex comprising many different
components, the capacity is expressed not by a single
number but by means of a graph model with individual
capacities of the components
[8].
The admission control
relies on finding a delivery path from the storage
devices to the selected network interface and reserving
appropriate capacities
on
all components on this path for
normal playback. The admission control may also rely on
resource-optimization techniques, e.g., batching and
caching. VCR control operations (e.g., pause, resume,
fast-forward) introduce new challenges for efficient use
of resources. Resources may be released and reacquired
upon resumption. However, it may not be possible to
guarantee that resources are available upon resumption.
For example, a new playback stream must be created upon
resumption of a client stream that was originally served
via batching. In large-scale servers, a small amount of
capacity may be set aside as contingency capacity for
dealing with VCR control operations
[18].
In addition to addressing the above resource
optimization issues, the next generation of multimedia
servers must address the challenges in retrieval of
composite multimedia documents.
A composite multimedia
document consists
of
many different parts (e.g., video and
audio clips, image, text, and data), with very different
storage and bandwidth requirements, that are to be
presented in a synchronized fashion. Therefore, the
bandwidth requirement varies over time. Fine-granularity,
time-varying advanced reservation of resources along with
prefetching of data can be used to improve resource
utilization
[19].
The issues must be addressed both at the
clients and at the servers. The prefetch schedule for
various media objects should also take into account the
bandwidth fragmentation in a server where different
components may be located in different storage devices.
Network challenges
Network subsystems create delivery paths from the
multimedia servers to the individual clients, and transport
the media objects. To avoid long latency and the need for
large client buffers, some media objects (e.g., large video
and audio files) are streamed isochronously to the clients
from the servers. [Note, however, that not all media delivery
requires isochronous streaming, as is the case when the
user browses noncontinuous media (e.g., text, image).]
Table
1
illustrates the Open System Interface
(OSI)
layers
and their services that should be addressed for end-to-end
multimedia applications. Starting from the lowest layers,
one finds challenges that are directly or indirectly related
to providing higher quality of service to the user.
Networks, covering the lowest four layers, have to meet
several challenges in the direction of multimedia services.
New technologies are required to bring high bandwidth to
the user. In business environments there is typically a
LAN attachment for each user station, which provides
shared or point-to-point bandwidth
of
the order of
10 Mbis or better. However, the network to the home is
currently limited to a few tens of Kbis (or to 128 Kbis
in the case of ISDN), because of the current telephone
network infrastructure. The evolution of technologies such
as ADSL
[20, 211
and HFC (CATV) [20, 211 will bring
bandwidth of the order of Mbis to the home, which is a
requirement for the successful deployment of real-time
multimedia to the home.
Raw bandwidth is not enough for effective delivery of
multimedia services, especially when this bandwidth is
shared among several systems or applications; it is
necessary to provide mechanisms that achieve delivery of
voice and video information isochronously,
so
that the
corresponding network connections allow users to enjoy
flawless delivery of media information. The general
concept of
QoS,
which has been introduced to broadband
ISDN, is used in multimedia applications. Although the
term
QoS
is general, it implies all of the properties that
are required for a flawless end-to-end service, Le., delivery
of information isochronously,
so
that the end user
experiences a continuous flow
of
audio and/or video
without interruption or noticeable problems of degraded
quality.
Network technology and the communication protocol
stack(s) used for multimedia information transmission
clearly play an important role in achieving the above
goals, i.e., to provide high bandwidth to the user with the
appropriate
QoS.
The wide spectrum of technologies in all
areas of networking-local, metropolitan, and wide-area-
require the development
of
interconnecting systems
(adapters, bridges, routers, switches, etc.), which support
high-speed communication among heterogeneous or
similar networks with low latency and low cost. The
challenges in this area are numerous: minimization of
data-transmission and data-reception overhead in order
to preserve link bandwidth for applications
[22,
231, low-
latency protocol processing [22,
24,
251,
and high-speed
routing [26,
271,
to mention a few. These problems
originate from data networking; the stricter latency
requirements of video and audio, in conjunction with the
differing standards that may be adopted at the various
networks, impose even stricter requirements. For
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noncontinuous, media-based applications, latency is often
far more important than jitter, since it may affect the
interactive response time. For certain networking
technologies (e.g., cable modem with asymmetrical
bandwidth, using TCPIIP), this latency can be quite high.
Depending on the level and protocol stack used for
the service, different problems may arise; for example,
transmission over the Internet or intranets with the
use
of
the currently widespread TCPiIP protocol suite does not
guarantee in-time delivery of time-sensitive information,
while MPEG** transmission with the use of the
AAL-5
protocol over an
ATM
network requires that the network
have bounded jitter
[21].
Considering that one of the main targets of multimedia
applications is provision of services to users in the same
fashion as telephone service, e.g., in kiosks and public
multimedia terminals, it is imperative that the network
infrastructure support security to appropriate levels, in
order
to
protect customers and ensure privacy. Tamper-
free systems, efficient authentication mechanisms, and
efficient and reliable transmission of encrypted
information are
a
necessity in such environments. In
environments where information is transmitted encrypted
and/or encoded (for compression), special attention has to
be
paid to the recovery of lost information in the network.
Client-design issues
The design of the client will,
as
always, be dominated by
questions of cost, functionality, and comfort. There are
several possible forms for the client device: an upgraded
television set (with internal or external “set-top’’
capability), an optimized personal computer (a network
computer with video capability), or a full-fledged personal
computer.
If
the control device is shared by all access
devices in the household as part of
a
residence gateway,
higher functionality may
be
possible than
if
the circuitry
must be replicated in each of the many TVs in
a
residence. The pressure to restrict the amount of RAM
and video-processing power will continue for some years,
but limiting buffer sizes and local computing will affect
the load on the network. (Small buffers and low
processing capability cannot handle highly compressed
video, Le., compression across multiple frames. Also,
prefetching and/or double buffering are required to
maintain the quality of the displayed image, Le.,
jitter reduction, smoothing.) Many functions can
be
implemented most easily
if
there is significant local
secondary storage, but servicing of moving parts, such as
disks, in
a
home-video environment could be a detriment
to sales.
The restrictions on local capabilities will certainly affect
which functions are performed well locally and which
depend on server or network support. Classic VCR control
operations can be implemented in many different ways
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[17,
181;
the tradeoffs depend crucially on the split of
capability throughout the system. For example, the server
can respond to the commands or switch from VOD to
NVOD mode,
an
intermediate node can store entire
streams, or the client can manage a cache.
There are
a
variety
of
physical methods for enabling
user interaction, ranging from standard infrared remote
controls to upgraded remote controls to traditional
computer pointing devices (e.g.,
a
mouse, TouchPoint).
Occasionally, alphabetic or numeric inputs are required,
at which time
a
real keyboard or keypad is desirable. In
addition, audio and video inputs (for video conferencing)
will be increasingly common, resulting in significant
implications for upstream bandwidth and control.
Apart from the above hardware considerations,
decisions about the software interfaces, control paradigms,
and operating system, such
as
which functions will be
static and which will
be
loaded with the content or upon
need, will have significant impact on cost and usability of
the client.
A
fixed set of capabilities is easy to manage but
restricts future upgrades and improvements in types of
content that can
be
viewed. As multimedia applications
evolve from simple replay to the inclusion of complex
search
[28-301
and simultaneous streams
[19,
31-33]
and
further to personalized environments, the client devices
(e.g., set-top box, camera, microphone) are likely to be
difficult to use. This will result in challenges with regard
to optimizing resources and avoiding misbehavior and
mischief, just as with current personal computers.
Application-design issues
Future multimedia applications will utilize valuable and
enjoyable types of information, including multiple audio
and video streams and time-, user-, and data-dependent
behaviors. Multiple applications that operate
on
the same
data will have to manage information, analyze images,
search for appropriate items, and mesh live, pre-recorded,
and interactive streams. The software framework must
make it easy for application developers
to
create software
that satisfies these and other needs.
Creating advanced content will become increasingly
challenging. It has always been difficult to produce videos
that are pleasant to watch. Advanced tools (e.g., for
authoring multimedia content
[31,
321)
will be required to
make it possible to combine multiple streams in attractive
ways that have maximum impact. However, addressing
human perceptions and psychological effects of
a
composition will always remain the realm of creative
artists.
Searching image, audio, and video data is far more
difficult than doing the same for text, but the rewards can
be
correspondingly higher. The adage “A picture is worth
a thousand words” suggests not only the higher value that
people put on multimedia data, but also the higher cost of
A.
DAN, S. FELDMAN,
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181
image and video data. Approaches to finding desired
information include creation and analysis of text
annotations
[28,
291,
examining reduced versions of
the video (thumbnails or key frames)
[28],
and full-
scale analysis of high-resolution data
[30].
Practical
considerations force
us
to maximize the value received
from a small amount of computation. The requirements
become particularly onerous in interactive and real-time
situations such as push technology
[34],
browsing, and
interactive navigation in large sets of multimedia data
~301.
Presenting the information is also difficult, especially
when system and network capabilities are limited.
“Best-
effort” networks
(with no guarantee of on-time delivery)
create challenges for synchronizing audio and video
substreams and require adaptation to feedback about user
behavior as well as network and server performance. The
adaptation may take into account
QoS
measurements by
the operating system and other system components
[35],
heterogeneous media
[36],
and heterogeneous
environments
[37].
Managing controlled collaborations
and teleconferences with many audio, video, and data
streams is even more challenging
[38,
391.
In the future,
people will want even more complicated composite moving
media, with complex constraints on location and timing
of the various parts
[31-331.
Interpretations of media data can also vary from
user to user. Thus, there is a need for a framework to
accommodate views of different users on the same data
and to provide mechanisms for creating and updating
views. The BRAHMA
[29]
framework proposes an
approach for annotating media data (i.e., creating views)
via user-defined attribute-value pairs for hierarchical
organization and retrieval of media data.
data. Conventional
virtual reality
and
3D
applications,
including those based on virtual reality markup language
(VRML), allow continuous movement
of
the viewpoint but
often suffer from poor performance, crude
3D
models,
large data files, low-quality rendered images of synthetic
scenes, and the need for expensive hardware. PanoramIX
[40]
alleviates these problems by employing image-based
rendering algorithms. Although the viewpoint is restricted
to discrete points in space, the “look-around performance”
is much better, the resulting images are very realistic, the
data files are relatively small, and no special hardware
is
needed. In addition, PanoramIX provides
a
composite-
media environment for embedding and hyperlinking
disparate media types, such as streaming audio, video,
1D-3D
sprites, and synthetic
3D
objects
[40].
Finally, virtual views can be created from
a
set of image
Summary and conclusions
Up to now, the lack of infrastructure for delivery of high-
quality video, the weakness of supporting technologies for
A. DAN,
S.
FELDMAN, AND
D.
N. SERPANOS
easy content creation, the absence of experience with
the benefits of futuristic multimedia, and a variety
of economic factors have impeded the widespread
deployment of multimedia applications. Experience with
video on the Web and availability of the Internet for
disseminating low- and medium-bandwidth products are
breaking down these barriers. People now accept the
enormous value of widespread use of multimedia
technologies to support societally desirable, financially
profitable, and personally rewarding services such as
distance-independent learning, low-cost video telephone
service, improved customer-relationship and help services,
new forms of entertainment and interactive games, and
new types of electronic commerce (such as tourism, real-
estate, and merchandise sales). There are still many
technology barriers, but the papers in this issue of the
IBM Journal
of
Research and Development
demonstrate
that we are making significant progress at overcoming
them.
Acknowledgments
We thank Marc Willebeek-LeMair, Nelson Manohar, Jai
Menon, William Pence, Junehwa Song, and anonymous
referees for their helpful comments and feedback.
**Trademark or registered trademark of Moving Picture
Expert Group.
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1,
99-109
(1993).
M. G. Kienzle, R. R. Berbec, G. P. Bozman,
C.
K. Eilert,
M. Eshel, and R. Mansell, “Multimedia File Serving with
the OSi390 Lan Server,”
IBM Syst.
J.
36,
No. 3, 374-392
(1997).
A. Dan,
S.
Dulin,
S.
Marcotte, and D. Sitaram,
“Multimedia Resource Management in OSi390 LAN
Server,”
IBM Syst.
J.
36,
No. 3, 393-410 (1997).
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28.
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30.
System Support for a Video-on-Dcmand File Service,”
ACM Multimedia Syst.
3, No. 2, 53-65 (1995).
A. Dan, D. Dias, R. Mukherjee, D. Sitaram, and
R. Tewari, “Buffering and Caching
in
Large Scale Video
Servers,”
Proceedings of IEEE COMPCON,
San Francisco,
1995, pp. 217-224.
A. Dan and D. Sitaram, “An Online Video Placement
Policy Based on Bandwidth to Space Ratio (BSR),”
Proceedings of ACM SIGMOD’95,
San Jose, May 1995,
D. Serpanos, L. Georgiadis, and A. Bouloutas,
““Packing: A Load and Storage Balancing Algorithm
for Distributed Multimedia Servers,”
IEEE
Trans. Circuits
&
Syst. for Video Technol.
8, No.
1,
13-17 (February
1998).
A. Dan, M. Kienzle, and D. Sitaram, “Dynamic Policy of
Segment Replication for Load-Balancing in Video-on-
Demand Servers,”
ACM Multimedia Syst.
3, No. 3, 93-103
(July 1995).
A. Dan, D. Sitaram, and P. Shahabuddin, “Dynamic
Batching Policies for an On-Demand Video Server,”
ACM
Multimedia
Syst.
4,
No.
3, 112-121 (June 1996).
L. Golubchik, J. C.
S.
Lui, and R. Muntz, “Reducing
I/O
Demand in Video-On-Demand Storage Servers,”
Proceedings of ACM SIGMETRICS,
1995, pp. 25-36.
A. Dan and D. Sitaram, “Multimedia Caching Strategies
for Heterogeneous Application and Server Environment,”
Multimedia
Tools
&
Appl.
(special issue: The State of the
Art in Multimedia)
4,
No. 3 (1997).
A. Dan, P. Shahabuddin, D. Sitaram, and D. Towsley,
“Channel Allocation Under Batching and VCR Control in
30, No. 2, 168-179 (November 1995).
Video-On-Demand Servers,”
J.
Parallel
&
Distr. Computing
J. Song, A. Dan, and D. Sitaram, “Efficient Retrieval of
Composite Multimedia Objects in the JINSIL Distributed
System,”
Proceedings
of
ACM SIGMETRICS,
Seattle, June
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(special issue: Reshaping
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S.
Davie,
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A
System
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1996.
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Subsystems for High Speed Networks,”
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Magazine
6,
No. 4, 40-46 (July 1992).
C. Partridge,
Gigabit Networking
(Addison-Wesley
Professional Computing Series), Addison-Wesley
Publishing Co., Reading, MA, 1993.
D. Serpanos, “Protocol Processing in High-speed
Communication Subsystems,”
Proceedings of High Speed
Networks ’93, the 5th International Conference
on
Data
Communication Systems and Their Performance,
Raleigh,
NC, October 1993, pp. 351-360.
A. Brodnik,
S.
Carlsson, M. Degermark, and
S.
Pink,
“Small Forwarding Tables for Fast Routing Look Up,”
Proceedings of ACM SIGCOMM,
September 1997,
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and Retrieval Architecture for Hierarchical Multimedia
Annotation,”
Proceedings of Multimedia Information
Systems,
West Point,
NY,
September 1996, pp. 25-29.
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33.
N.
R. Manohar and A. Prakash, “The Session Capture
and Replay Paradigm for Asynchronous Collaboration,”
Proceedings of the European Conference
on
Computer
Supported Cooperative Work,
Stockholm, September 1995,
pp. 149-164.
31.
M.
Kim and J. Song, “Multimedia Documents with Elastic
32. M. Cecelia-Buchanan and P. T. Zellweger, “Scheduling
34. PointCast Home Pagc,
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35. N. R. Manohar and A. Prakash, “Dealing with
Synchronization and Timing Variability in the Playback of
Interactive Session Recordings,”
Proceedings
of
the 3rd
ACM International Multimedia Conference,
San Francisco,
1995, pp. 45-56.
36.
N.
R. Manohar, M. Willebeek-LeMair, and A. Prakash,
“Applying Statistical Process Control to the Adaptive
Rate Control Problem,”
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Annual Symposium, Multimedia Computing and Networking
Conference,
San Jose, 1998, pp. 42-56.
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Networks Using an Adaptive Framework,”
IEEE
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pp. 72-81 (November 1997).
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E.
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G.
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Web-Enabled Multimedia Teleconferencing System,”
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37. M. Naghshineh and
M.
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39.
C.
Bisdikian,
S.
Brady, Y.
N.
Doganata, D. A. Foulger,
Received January
26,
1998;
accepted
for publication
February
2,
1998
A. DAN,
S.
FELDMAN, AND D. N. SERPANOS
Asit Dan
IBM
Research Division,
Thomas
J.
Watson Research
Center,
P.O.
Box
704,
Yorktown Heights, New York
10598
(asit@us.ibm.com).
Dr. Dan received a B. Tech. degree in
computer science and engineering from the Indian Institute of
Technology, Kharagpur, India, and the M.S. and Ph.D.
degrees from the University of Massachusetts, Amherst, in
computer science and computer engineering, respectively. His
doctoral dissertation on performance analysis of data sharing
environments received an Honorable Mention in the 1991
ACM Doctoral Dissertation Competition and was published
by the MIT Press. He has published extensively on the design
and analysis of video servers as well as transaction-processing
architectures, and served
as
the tutorial chair for
SIGMETRICS '97 and various other program committees. He
is
a
major contributor to various IBM products in the above
areas, holds several top-rated patents, and has received two
IBM Outstanding Innovation Awards and five IBM Invention
Achievement Awards. Currently, Dr. Dan is leading a project
on the development of COYOTE middleware for supporting
long-running transactional applications across autononous
business organizations.
Stuart
1.
Feldman
IBM
Research Division,
Thomas
J.
Watson Research Center,
P.O.
Box
704,
Yorktown Heights, New
York
10598
(sif@watson.ibm.com).
Dr. Feldman received an
A.B. degree in astrophysical sciences from Princeton
University and a Ph.D. in applied mathematics from the
Massachusetts Institute
of
Technology. He spent ten years
in
computer science research at Bell Laboratories as a member
of
the original UNIX research team. He spent the next
11
years at Bellcore, where he held several research management
positions in software engineering and computing systems. He
joined IBM in 1995 at the Thomas
J.
Watson Research
Center as Department Group Manager of Network
Applications Research. He has recently been named director
of
the newly established IBM Institute for Advanced
Commerce in Hawthorne, New York, which brings together
leaders in business and academia to research the impact of
emerging technologies on the future
of
business and
commerce. Dr. Feldman
is
an ACM Fellow, an IEEE Fellow,
and a member of Phi Beta Kappa and Sigma Xi.
Dimitrios
N.
Serpanos
Department
of
Computer Science,
University
of
Crete,
P.
0.
Box
1470, GR-71110
Heruklion, Crete,
Greece (serpanos@csd.uch.gr).
Prof. Serpanos received a
Diploma in computer engineering and information sciences
from the University of Patras, Greece, in 1985 and a Ph.D. in
computer science from Princeton University in 1990. He
joined the IBM Research Division at the Thomas
J.
Watson
Research Center in 1990 as a Research Staff Member,
working
on
high-bandwidth systems and interactive media
solutions. In 1996 he joined the faculty of the Department of
Computer Science of the University of Crete in Greece; he
also works at the Institute
of
Computer Science of the
Foundation for Research and TechnologyHellas
(ICS-FORTH). His research interests include high-speed
interconnections, high-speed communication systems, and
multimedia systems. Prof. Serpanos has received awards from
IBM, holds two
U.S.
patents, and has published several
papers. He is a Senior Member of the Institute of Electrical
and Electronics Engineers (IEEE) and a member of the
Association for Computing Machinery (ACM), the New York
Academy
of
Sciences, and the Technical Chamber of Greece.
A. DAN,
S.
FELDMAN, AND D. N. SERPANOS IBM
J.
RES. DEVELOP. VOL.
42
NO.
2
MARCH 1998
